This glossary is not intended to be complete or all-encompassing.
It covers common terms seen on InetDaemon.com and elsewhere dealing with computers
and data communications technologies. Definitions are from InetDaemon himself--be warned.
"When I use a word," Humpty Dumpty said, in a rather scornful tone,
"it means just what I choose it to mean - neither more nor less."
"The question is," said Alice, "whether you can make words mean
so many different things."
"The question is," said Humpty Dumpty, "which is to be master
- that's all."
Lewis Carroll - Through the Looking Glass.
- A-Polarity (A-Pol)
- Circular polarity radio antennas are described as having either A-polarity
or B-polarity. A-polarity antennas use clockwise (right hand) circular polarity.
- Term used to describe a logical framework used for solving a particular
computer problem via programming. Ex. The 'shortest path' algorithm is logic
that calculates the shortest path between two points.
- Autonomous System (AS)
- An autonomous system is a network or set of networks under one administrative
authority such as a company or other organization.
- Autonomous System Number (ASN or AS#)
- An AS number is assigned by the American
Registry for Internet Numbers (ARIN). This number must be unique, and be assigned
to only one autonomous system. Companies and other organizations may have
multiple AS numbers, provided they can demonstrate a need for this number.
AS numbers are used by BGP to identify autonomous systems,
as well as internal and external connections.
- Autonomous System Path
- This is a list of AS numbers which map the path through
Autonomous Sysstems to the destination network. AS Paths are included in BGP
Update Messages along with NLRI information as part of the routing protocol
update announcements in BGP.
- The size of the signal output. In electrical systems this is voltage, in
radio systems this is radiated power.
- AS Path
- See Autonomous System Path.
- Asynchronous Transfer Mode (ATM)
- Asynchronous Transfer Mode (ATM), also referred to as Broadband-ISDN is
a standards-based networking protocol utilizing 53 byte cells, and supports
virtual connections, dynamic path switching and quality of service.
- Bulletin Board System (BBS)
- Bulletin Board System. A dial-up computer service consisting of a limited
number of modems connected to a computer running Bulletin Board System software.
Users may exchange e-mail with each other, play games, chat or communicate
with other BBS's if the sysop has set up a mail gateway to another BBS. The
invention of BBS's is generally credited to Ward Christiansen. InetDaemon
once belonged to a BBS named Genesys run by SysOps Viper and EmJay.
- B-Polarity (B-Pol)
- Circular polarity radio antennas are described as having either A-polarity
or B-polarity. B-polarity antennas use counter-clockwise (left hand) circular
- Backwards Explicit Congestion Notification (BECN)
- Used in frame relay to signal to the downstream
device that the connection is congested.
- Often used erroneously to describe the total bit per second data rate, this
term actually refers to the total ammount of voltage or signal spectrum that
can be used to transmit data. The greater the range of values, the greater
the data transfer rate.
- Number of symbols or symbol changes per second. Each symbol can cary more
than one bit, so any measure of baud rate is not equivalent to bit
rate or bandwidth. For example, telephone voice
lines send 8,000 symbols per second and each symbol represents 8 bits. Multiplying
the symbol rate times the bits per symbol gives 64,000 bits per second and
the baud rate is 8,000.
- The binary number system consists of the digits 0 and 1. This makes binary
especially suited for working with electronic circuits that can have only
two values: on and off.
- Bit Rate
- Number of bits per second transmitted over a communications medium. Often
abbreviated as bps, kbps, mbps, gbps, tbps.
- Black Hole
- Black holes are the roach motels of the Internet.
Black holes occur when
a range of IP
(an IP block) is routed to a network where none of
the addresses are assigned, and are not in use. This effectively causes the
traffic to be dropped into what looks like a 'black hole'. Packets go in,
but don't come out. Black Holes are typically caused by improper routing announcements
of prefixes not assigned to an AS.
- Bootstrap (boot)
- The process of starting up, usually unaided. Term refers to 'pulling yourself
up by your bootstraps'.
- Border Gateway Protocol
- BGP is a dynamic, exterior gateway protocol used for exchanging 'best-path'
route information between autonomous systems. BGP does not exchage explicit
hop-by-hop route information, but rather AS-paths and
- Computer chips can't be interconnected that easilly by themselves. Chips
have to be inserted into specially designed pieces of fibrous plastic called
"breadboard". The breadboard has metal wires running in neat little
rows that connects all the chips together, so in today's computers, it's easier
to work with 'boards' than it is with 'chips'. On most computers, the breadboard
is the green board all the chips are soldered into. If you look closely, you
can even see some of the wires inside it.
- Broadcast Storm
- A broadcast storm usually occurs in bridged netwrorking environments where
broadcast traffic is being re-transmitted back and forth on the linked segments.
Since devices are sending out repeated broadcasts, all available network capacity
is used up transmitting these broadcasted frames, and none of the nodes are
able to transmit or receive responses, thus initiating more broadcasts.
- A transmission system that utilizes multiple frequencies to transmit data simultaneously. Often misused when referring to the speed of a connection.
- Central Processing Unit, or simply 'processor'. Processors process 'instructions'
and 'execute' program code.
- Carrier (also 'common carrier')
- Telecommunications provider, usually denoting an organization with nationwide
or worldwide communications capability.
- Carrier Signal
- An electromagnetic emission used as a baseline signal for carrying information.
- Central Office
- A central office is a building or location where all telephone voice channels
are aggregated together for multiplexing over a trunk line to another central
office in a remote location.
- Connectionless protocols do not bother to set up or check for an end-to-end
connection. Connectionless systems simply transmit and don't worry whether
the receiver is ready or available. TV, Radio, Walkie-Talkies and CB's are
good examples of Connectionless systems. In the Internet arena, UDP is a connectionless
- A connection-oriented protocol establishes end-to-end connections for communication.
- A datagram is a unit of data of variable length. Data is produced by computer
users, and chopped into pieces by some piece of software running at the Transport
layer or above. It would be most correct to say that datagrams are put
into packets, and that packets are put into frames.
- Data Circuit-terminating Equipment (DCE)
- Sometimes also seen as Data Communication Equipment. The DCE device is most
commonly the device providing the communications facilities. It is the responsibility
of the DCE interface to set the clock rate for the signalling so that the
end stations (DTE's) can establish synchronization with
the signal and communicate.
- Data Terminal Equipment (DTE)
- The DTE is usually and end station, the device using the communications
- The process of descrambling an encrypted sequence of data using an encryption/decoding
- Destination Address
- Address of the receiving device.
- Dynamic Host Control Protocol - Protocol that is a member of the
Protocol suite. Used to assign
to hosts as they bootstrap
and connect to the network.
- End Of File. A sequence of characters used to indicate the end of a data
- End Of Line sequence. A set of characters used to indicate the end of a
logical line of data.
- To convert data into a specific format
- As in small-endian and big-endian. Computing term referring
to the order in which bytes are transmitted, either low order or high order
bits are sent first. This is a reference to Gulliver's Travels by
Danny Cohen in his paper "On Holy Wars and a Plea for Peace". The
order in which bits are transmitted becomes vitally important in comptuer
to computer communications. Bits sent in what is percieved to be reverse order
can cause data to be lost or scrambled and makes communication nearly impossible.
Very heated discussions were very common regarding whether big-endian or little-endian
transmission order was better, thus the paper and the call for peace.
- Exterior Gateway Protocol (EGP)
- A routing protocol used to communicate between networks administrated and
owned by different organizations. Compare to Interior Gateway Protocol.
- The process of adding a header (and possibly trailing) information to a
piece of data for the purposes of passing it through some other system. Encapsulation
is used by most computers today when communicating with the Internet. Data
is encapsulated in TCP
or UDP, then encapsulated in
IP and then transmitted over the
- The process of scrambling data in an ordered format so that it can be descrambled
at the other end. Decryption of encrypted data requires the key which was
used to encrypt the data. Larger/longer keys produce better encryption.
- Forward Error Correction
- [Radio Frequency] FEC is used in simplex communication to attempt to recover
from symbol errors in a communications datastream.
- Forward Explicit Congestion Notification (FECN)
- FECN is used in frame relay to signal to the upstream frame relay device
that there is congestion in the forward path.
- [Hardware] A frame is a unit of data that varies in size. It is the unit
that is created by the Data Link layer.
- [HTML] A frame is a piece of a browser window that is created using the
HTML 'frame' command within a 'frameset'.
- Frame Relay
- The second generation of packet switching technology put to use in the telecommunictions
arena after X.25. Frame Relay is a packet-switching technology
that provides non-reliable cut-through switching of frames through the network.
Also known as 'fast packet'.
- Number of times per second a signal regenerates itself at a peak amplitude
expressed in hertz. In general, the higher the frequency,
the greater the rate it can transmit data.
- A gateway is a device used to forward data from the local network to other
networks. Synonomous with the term 'router'.
- The name of the protocol standards document defining video over
used in IP
- High Speed Serial Interface. Cisco proprietary protocol adopted by many
other network gear manufacturers. Supports up to 52Mb/sec.
- A measurement of the number of cycles per second in a signal. Higher frequency
signals have higher hertz rates.
- A numbering system consisting of the digits 0 through 9 and the letters
A-F. This allows each column in a Hexadecimal
number to represent sixteen different values. Usually designated in literature
by the character combination "0x" (zero x).
- A host can be any device on a network that provides access or service. Host
is a general term usually used to refer to a computing device. The term 'host'
is used synonymously with 'computer' and 'node'.
- Implement (implemented, implementation)
- [Programming] A particular algorithim written into computer software as
program code. ie: "It's an implementation of Diffie-Hellman"
- [Telecom.] To install and configure a communications circuit. Most often
used when discussing the process of installing a circuit for a telecommunications
- Interior Gateway Protocol
- A routing protocol used for exchanging routes between networks that are
under a single administrative control or owned by a single organization.
- Joint Electronic Devices Engineering Council. A group of chip manufacturers
who have formed a committee to standardize size, form factor and connector
issues for chips, mostly for RAM (memory).
- "Just a Bunch Of Disks" - a series of disks not utilizing a mass
storage architecture such as RAID.
- A small metal bracket used to connect two pins and thereby create a short
between them. The term jumper is used for both the bank of pins, and the metal
bracket used to 'short' them.
- Keyboard Video Mouse switch. A special device used to enable multiple computers
to share one keyboard, video display and mouse. Useful in server environments
or where multiple computers are in use.
- Kilobit (Kb)
- 1,024 bits. A measure of size, most often used when referring to data transfer
rates such as with modems (56 Kbps).
- Kilobyte (KB)
- 1,024 bytes. A measure of size, most often used when referring to memory
or data storage and occasionally data transfer rates.
- Logical Link Control - Layer of the 802.x protocols specifying the process
of communicating with the physical link.
- Local Area Network. Any network located in a single facility, usually restricted
to one building.
- LAPB (Link Access Procedure, Balanced mode)
- LAPB is a data-link layer protocol
that provides ordered, reliable communication between
DCE and DTE devices in an X.25 telecommunications network.
- LAPD (Link Access Procedure, D channel)
- This is the data-link layer protocol used to control the 'D' or 'data' channel
on an ISDN BRI connection. Also known by the ITU specification document numbers
Q.920 / Q.921
- The term link is used loosly to describe a physical or virtual network connection.
- Link state routing algorithms are aware of the performance
of physical network connections when calculating the shortest path to a destination.
- The Media Access Controller (MAC) is a chip
that controls access to the physical media (copper wire, optical fiber
or a radio frequency). Often, a permanent address is 'burned in' to the memory
of this controller. This address is also referred to as a 'MAC'.
- Shortened form of the word 'MacIntosh', as in the phrase "Friends don't
let friends buy Macs."
- Metropolitain Area Network. A network serving one city or metropolitain
- This is what all the other smaller boards plug into, so sometimes it's
called a MOTHERBOARD. Mainboards have 'expansion slots' allowing the computer's
capabilities to be 'expanded' by adding on additional hardware. Sound, Video
and Input/Output can all be 'expansion' devices.
- Maximum Transmission Unit (MTU)
- The MTU is a term used to refer to the maximum frame size for a particular
network inerface card.
- See 'Mainboard'.
- A network is a group of computers connected to each other over a common
- Network Interface Card (NIC)
- Network Interface Cards are components used in computers to allow them to
connect to the network wiring.
- A more general term referring to any device attached to a communications
or data network.
- An octet is eight binary bits.
- A number system which uses only the digits 0-7 as symbols.
- A packet is the term used to describe units of data that are created by
the Network Layer.
- All electromagnetic signals travel in waves and thus the trigonometric functions
of sine and cosine can be used to describe/calculate their behavior. The term
phase is used to describe the value of the wave at a particular instant in
time. By 'shifting' a signal's phase, data can be encoded.
- Positive or negative voltage in electrical systems
- [Radio Frequency] clockwise or counter-clockwise behavior
- A physical connector, such as for serial or ethernet connections.
- A number identifying a specific virtual connection.
- An application converted to run on a computer it was not originally designed
- Q.920 / Q.921
- See LAPD
- Quadrant Phase Shift Keying (QPSK)
- Typically used in radio frequency modulation, QPSK utilizes shifts in frequency
phase to encode data into a carrier signal.
- Quadrature Amplitude Modulation (QAM)
- This modulation technique is most often seen in computer telephone and cable
modems. QAM is a frequency-amplitude modulation technique, that uses frequency
and amplitude changes to encode data into the carrier signal.
- Redundant Array of Inexpensive Disks - A system of connecting a large number
of smaller (thus less expensive) disks together for mass storage of data instead
of buying a single large drive. RAID can be configured for redundancy (mirroring)
and performance (striping). The different RAID configurations are referred
to as RAID levels: 0, 1, 0+1, 3, 5).
- Random Access Memory. Temporary storage on the chips inside the computer.
They can store information only as long as there is electrical power.
- A RAM-disk is a simulation of a hard disk in RAM. This allows the system
to access higher memory as if it were stored on a disk. This is the opposite
of virtual memory.
- Read Only Memory. These chips store what is often referred to as 'microcode'
designed to perform critical functions, usually at bootstrap. Smaller devices
rely upon ROMS for more complex functions.
- The term 'reliable' refers to a service or protocol that provides for recovering
from errored transmission states. Examples of techniques used to assure reliability
are Acknowledgements and error-checking. See also: unreliable.
- A network layer process that forwards
packets from a source network to a destination network.
- Routing Protocol
- A standard way of routing packets, which usually is
implemented as a program that runs on a device that performs routing.
There are two main categories of routing protocols, interior
gateway protocols and exterior gateway protocols.
- Device from the earliest days of the telephone. These were dedicated half-duplex
telephone connections across trunk lines between telephone operations centers.
Two-way communication required a second line strung back in the opposite direction,
or a 'round-the-horn' relay back to the originating center. Engineers would
pick up the handle and 'shout down' to the next telephone operations center
during outages and emergencies.
- An electromagnetic transmission used for the purpose of transmitting information.
This transmission can be either electrical, radio freqency or light.
- Source address
- The address of the machine transmitting data (doing the talking). Note that
in two-way communication the sender and receiver alternate roles during the
- The total range of frequencies falling into a particular category (visible
light spectrum, radio frequency spectrum).
- Superframe (SF)
- Superframe is a telecomunications linecoding scheme used for controlling
the transmission of digital data over T1 lines. It provides for 24 timeslots
of 64kbps each and an additional bit-stuffed control channel of 8 kbps.
- In the computing field, symbols are used to represent patterns of data bits.
Symbols themselves are represented by specific modulation states within a
- Symbol Rate
- Symbol Rate refers to the number of symbols that are transmitted in one
second. From the symbol rate, one can calculate the bandwidth (total number
of bits per second) by multiplying the bits per symbol times the symbol rate.
- Term used to classify various multiplexing levels in US and US-compatible
telecommunications networks (ie. T1, T2, T3 etc.)
- See Transmission Control Protocol.
- See Telephone Operations Center
- Telephone Operations Center
- See Central Office
- 1. A software application emulating a teletype terminal interface to a computer.
2. Teletype-style device providing an input/outsput mechanism composed of
a monitor and keyboard or other input device that provides an interface to
a remote computer system.
- Of or situated on terra-firma (the earth). Also referred to as 'land-based'.
- Transmission Control Protocol
(TCP) is a reliable, connection-oriented protocol
used for transporting data across one or more networks.
- This term is used to mean that a protocol or service does not provide error-checking
or data-recovery mechanisms
- User Datagram Protocol
- User Datagram Protocol (UDP)
is an unreliable, connectionless
Transport Layer protocol used to transport
data accross one or more networks.
- VoIP /
Voice over IP
- Protocol that allows the encodes and encapsulates telephony data into
datagrams for transport over an IP
network such as the Internet.
- Virtual memory is the process of using hard disk space as if it were RAM.
This allows the computer to launch and run many more programs than it might
normally be capable of. Virtual memory takes advantage of the fact that humans
have difficulty doing more than one thing at a time. Thus, it is possible
to move programs which the user is running, but not actively using to the
hard disk while they are busy doing something else. Contrast this with a RAM-disk.
- Sometimes confused with frequency. Whereas
the term frequency is used to refer to an
electromagnetic signal at a particular wavelength, wavelength refers
to the physical distance of 1 cycle of the signal's waveform (from peak to
trough to peak). In microwave communications, the distance between waves is
measured in nanometers. Radio frequencies can be measured in miles.
- Wide Area Network (WAN)
- Wide area networks are networks that are usually not enclosed in a single
building. WANs can be as small as a college or company campus, or can span
the entire globe. Compare with LAN and MAN.
- The first true packet switching technology put into widespread use worldwide
in Telecommunications systems. X.25 utilizes X.121 addressing and LAPB
for ordered and reliable communication.
- X-modem was developed by Ward Christiansen for use with the first BBS.
X-modem transmits data in 128 byte blocks followed by a 1-byte checksum and
specifies a 1 second timeout on the data transfer connection.
- Yellow Alarm
- Telecommunications: Used in T1 communications over superframe
or extended superframe. A yellow alarm indicates that a Remote Alarm Indication
signal was received from the upstream equipment.
- The second data transfer protocol developed by Chuck Forsberg as an improvement
on X-Modem. Y-modem for use between computers connected
with modems. This protocol was faster and provides some error correction.
- Another serial data transfer protocol for use between modems deveolped by
Chuck Forsberg. Z-modem is faster, does not check for receipt of data and
adds the ability to resume an interrupted transfer. X-modem,
Y-modem and Kermit.
- ZIF socket
- Zero Insertion Force socket. These sockets are used for fitting the main
CPU to the mainboard. A lever is placed on the side allowing the processor
to be simply dropped into place. Once the lever is pulled down and secured,
the processor is held firmly in place.
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